StarChild Question of the Month for February 2000

Question:

Does the Sun move around the Milky Way?

Answer:

Yes, the Sun - in fact, our whole solar system - orbits around the
center of the Milky
Way Galaxy. We are moving at an average velocity of 828,000 km/hr. But even
at that high
rate, it still takes us about 230 million years to make one complete orbit
around the Milky
Way!

The Milky Way is a spiral galaxy. We believe that it consists of a central
bulge, 4 major
arms, and several shorter arm segments. The Sun (and, of course, the rest
of our solar
system) is located near the Orion arm, between two major arms (Perseus and
Sagittarius).
The diameter of the Milky Way is about 100,000 light-years and the Sun is
located about
28,000 light-years from the Galactic Center. You can see a drawing of the
Milky Way
below which shows what our Galaxy would look like "face-on" and the
direction in which
it would spin as viewed from that vantage point. Also shown, is the
location of the Sun in
the big picture view of our Galaxy.

It is interesting to note that recent observations by astronomers suggest
that the Milky Way
is in fact a "barred spiral galaxy", not just a "spiral galaxy". This means
that rather than a
simple spherical bulge of gas and stars at its center, it has instead a
"bar of stars" crossing
the central bulge. It might look something like the image shown below of
the barred spiral
galaxy known as NGC1073. But we still rotate around the center just the same!